Integrative Transcriptome and Machine Learning Analysis Uncovers Critical STAT3/GREM2 Signaling Mechanisms in Dexamethasone Treatment of Hashimoto’s Thyroiditis

Hashimoto's thyroiditis (HT) is a common autoimmune thyroid disorder influenced by genetic, environmental, and immunological factors. Current treatment primarily relies on thyroid hormone replacement therapy, yet the underlying mechanisms of the disease and its response to therapy remain poorly understood. Therefore, elucidating the molecular mechanisms of HT, especially in response to immunosuppressive agents, is essential for improving therapeutic strategies. In this study, we integrated transcriptomic profiling, machine learning, and experimental validation to elucidate the immunoregulatory effects of Dex in HT. Peripheral blood samples from healthy individuals, untreated HT patients, and Dex-treated HT patients were analyzed via RNA sequencing, with differentially expressed genes (DEGs) identified using the "limma" R package. Functional enrichment analyses (GO, KEGG, and GSEA) revealed that Dex treatment downregulated key immune and inflammatory pathways, particularly those involving cytokine signaling and the JAK-STAT axis. Integrative machine learning approaches (LASSO, SVM-RFE, and Random Forest) consistently identified GREM2 as a Dex-responsive gene, which was further validated in an independent cohort using correlation and ROC analyses, supporting its predictive value for treatment response. CIBERSORT analysis demonstrated substantial alterations in immune cell infiltration, including shifts in B-cell subtypes. Mechanistically, GREM2 was validated as a downstream target of STAT3 through dual-luciferase assays and siRNA interference. In vitro studies using LPS-induced Nthy-ori 3-1 thyroid cells confirmed that Dex exerts its anti-inflammatory effects by inhibiting STAT3 phosphorylation, thereby reducing GREM2 expression and downstream proinflammatory cytokines such as TNF-α, IL-1β, and CCL2. These findings highlight the STAT3/GREM2 signaling axis as a critical mediator of Dex's therapeutic action in HT and provide a mechanistic framework for its potential clinical application in autoimmune thyroid diseases.